a) Field of the Invention
This invention relates generally to an axle disconnect assembly for part-time four wheel drive vehicles and more particularly to vacuum-operated axle disconnect systems.
b) Description of Related Art
It is known to provide a part time four wheel drive vehicle that includes an axle disconnect mechanism in a front axle assembly. Such axle disconnect mechanisms include a vacuum motor and a shift fork assembly. The vacuum motor communicates with a vacuum source that is controlled by a two position solenoid valve. The fork shift assembly under control of the vacuum motor controls the axial shifting of a clutch collar between positions corresponding to coupled and uncoupled operating modes.
This conventional system has the drawback of an externally mounted vacuum motor that requires considerable extra space particularly when vehicle suspension travel is taken into account. The use of an externally mounted vacuum motor also necessitates the use of a fork shift assembly which adds to the cost and complexity of the prior art arrangement exemplified by this system.
It is also known that a part time four wheel drive vehicle may include an axle disconnect in the front axle assembly, wherein the axle disconnect is operated by a power shift mechanism. The power shift mechanism includes sealed envelopes in the form of expandable and contractible compartments that shift the axle disconnect into and out of engagement in response to a remote control valve. The sealed envelopes are offset from the axle housing. The shiftable drive gear couples and uncouples inner and outer drive shafts.
This power shift mechanism requires two sealed envelopes and numerous other parts operatively connecting the sealed envelopes with the shiftable drive gear. Moreover, such prior art axle disconnect systems do not provide a modular arrangement necessary for easy of manufacture, assembly and repair. Consequently these prior art arrangements are also complex and expensive to produce particularly when the difficulty of assembly is taken into account.
The need therefore exists for an axle disconnect arrangement and design that is simple in design, compact in construction and economical to package and manufacture.